Your sense of smell changes across your cycle: what the evidence shows

If food, perfume or a partner's skin smells different at certain points in the month, you are not imagining it, and you are not broken. Smell is one of the senses that has been measured across the menstrual cycle for more than seventy years, and the best summary of that research is that sensitivity rises a little around ovulation and dips a little during the period. The effect is real on average, small in size, and inconsistent from one woman to the next.

Two other things get folded into the same question and deserve separate answers. Your own scent can change across the cycle and in perimenopause, mostly through sweat and vaginal fluid, and that is ordinary. A strong or fishy odour from the vagina is not a hormonal quirk and usually points to an infection or an imbalance that has a treatment. This article takes the three apart: how your nose changes, how your body's smell changes, and which smells mean a swab rather than a shrug.

None of this can be predicted by an app. A cycle tracker can show you where a smell-related note fell relative to your period and ovulation estimate. It cannot measure your hormones, confirm that you ovulated, or tell you whether a new odour is harmless.

A woman with her eyes closed holding a bouquet of flowers to her face. Photo by cottonbro studio on Pexels.

Does the cycle really change how well you smell?

On average, yes, but the story is messier than most articles admit. Researchers measure smell sensitivity by finding the weakest concentration of an odour a person can detect, called the detection threshold. A lower threshold means a sharper nose.

The largest single study is from Navarrete-Palacios and colleagues, published in Biological Psychology in 2003. They tested 332 women once each, in one of four cycle phases, plus 15 women across a full cycle, using amyl acetate, a banana-like smell. Thresholds were lowest around ovulation and highest during menstruation, and the ovulatory-phase women out-detected every non-cycling comparison group, including men, girls before puberty, and women after menopause.

Not every study agrees. A 1991 study in Chemical Senses followed 14 women through their cycles with three odours and found no significant change in sensitivity at all. It did find that androstenone, a steroid found in sweat, was rated most pleasant around ovulation, which hints that what changes may be how odours feel rather than whether you detect them.

A 2014 meta-analysis in Anthropological Review pulled the threshold studies together. Thresholds were significantly lower in the fertile phase than in non-fertile phases, and the effect ran the same direction for food odours, musky odours and androgen steroids. It did not hold for phenylethyl alcohol, a rose-like smell. The authors concluded that the shift looks like a general by-product of the cycle's physiology rather than a system tuned to detect potential mates, which is the version usually told online.

Phase	What the threshold studies suggest	How confident to be
During the period	Least sensitive in the largest study; some studies found no change	Moderate
Around ovulation	Most sensitive on average across the meta-analysis	Moderate
Luteal phase	Higher thresholds and stronger intensity ratings in an 80-person 2013 study	Low to moderate
On the pill	Longer use linked to better test scores in the same study; only 20 users tested	Low

Why the luteal phase can feel different anyway

A lower detection threshold is not the same as smells feeling stronger. A 2013 study in Chemical Senses tested 80 people with the standard Sniffin' Sticks battery. Women in the luteal phase had higher thresholds than women in the follicular phase, so they were slightly less sensitive, yet they rated the test odour, n-butanol, as more intense. Being bothered by a smell and being able to detect faint traces of it are two different measurements, and they moved in opposite directions.

That fits what many people describe in the week before bleeding: nothing is faint, but the fridge, a colleague's lunch or a familiar fragrance is suddenly too much. If that aversion arrives with a headache, it may be part of a migraine rather than a smell change on its own. Our article on menstrual migraine covers the timing.

Does your own scent change too?

Probably, in small ways, and mostly through ordinary routes.

Sweat, which the NHS lists alongside exercise, hot weather, hormonal changes and some medicines as things that make body odour more noticeable
Vaginal fluid, which changes in volume and texture through the cycle, as described in our guide to cervical mucus and discharge
Menstrual blood, which has a smell of its own and mixes with discharge on pads and underwear

Research has also asked whether other people can smell where you are in your cycle. A 2012 study in Hormones and Behavior collected underarm scent samples on a low-fertility and a high-fertility day, with ovulation confirmed by luteinising hormone tests. Men told the two samples apart 61 percent of the time and preferred the high-fertility sample 56 percent of the time. Both figures beat chance, and both are close to it. Nobody is detecting your ovulation across a room.

What changes in perimenopause

Two threads run through the perimenopause forums: smelling things nobody else can, and smelling different yourself. The second has a well-documented mechanism. The NHS lists hot flushes and night sweats among the most common symptoms of perimenopause, and sweating is the most direct route to a change in body odour. Falling oestrogen also changes the vagina itself, and the NHS notes dryness, irritation and more frequent urinary tract infections in this stage, all of which can alter smell.

The first thread has less evidence behind it. Smelling smoke, burning or a chemical smell that is not there is called phantosmia, and the NHS lists its usual causes as colds, flu, COVID-19, sinusitis, allergy, nasal polyps and some medicines, with rarer neurological causes. Perimenopause is not on that list. If a phantom smell keeps coming back, or your sense of smell does not return to normal within a few weeks, the NHS advises seeing a GP, whatever your age. Our guide to perimenopause and period changes covers what else to expect.

Smells that mean infection, not hormones

Hormones change vaginal odour gently. Infections and bacterial imbalances change it sharply, and the two are not hard to tell apart once you know the signs. Both the NHS and ACOG single out the same smell.

What you notice	What it most often is	What to do
Strong fishy smell, often worse after sex or during a period, thin greyish-white discharge, little or no itching	Bacterial vaginosis, per the NHS and ACOG	See a GP or sexual health clinic; treated with antibiotics
Yellow-green, sometimes frothy discharge that may smell fishy, pain when peeing, soreness	Trichomoniasis, a sexually transmitted infection, per the NHS	Sexual health clinic; you and partners need treatment
Thick white lumpy discharge with itching and burning, usually no odour	A yeast infection, per ACOG	Pharmacist or GP; check before self-treating if it is your first time
Mild, slightly sour or tangy, varying through the month	Ordinary vaginal fluid	Nothing

The NHS notes that around half of women with bacterial vaginosis have no symptoms, that it often comes back, and that you are more likely to get it with a change of partner, an IUD, or perfumed products used in or around the vagina.

The most useful thing to know is what not to do. ACOG advises against feminine hygiene sprays, scented tampons and douching, and the NHS says the same about vaginal deodorants and washes. Products sold to fix vaginal odour disturb the acidic environment that keeps the balance in the first place. If the smell is strong enough that you are shopping for a product, it is strong enough to be swabbed.

When to see a doctor about a smell

Arrange a routine appointment if:

A fishy or foul vaginal odour appears, with or without a change in discharge
Discharge turns yellow, green, grey or frothy, or arrives with itching, soreness or pain when peeing
Your body odour changes from how it usually smells, or you suddenly sweat much more than before, which the NHS lists as reasons to see a GP
You smell things that are not there, or a lost or changed sense of smell has not recovered within a few weeks
You are pregnant and your discharge changes; the NHS asks you to tell a GP or midwife because bacterial vaginosis carries a small risk in pregnancy

If a strong smell comes with fever, pelvic pain or bleeding between periods, seek prompt medical advice rather than waiting for a routine slot.

What is worth writing down

Smell is one of the few symptoms almost no tracker offers as a tick box, which is not a great loss. A one-line note does the job better, because the useful information is the specifics.

What smelled different: food, perfume, a partner, your own sweat, discharge
Whether it was sharper or just more unpleasant, since the research says those are different things
Where it fell in the cycle, which your tracker supplies if the period dates are logged
Anything else at the time: a cold, a new medicine, a new partner, a change of contraception

Three or four cycles of that is enough to see whether a smell change keeps turning up at the same point. One cycle tells you nothing, and a pattern that does not line up with your cycle at all is a reason to look for a non-hormonal cause. Our guide to ovulation signs and their limits explains why no single body signal, smell included, confirms that you ovulated.

Frequently asked questions

Can a heightened sense of smell tell me I am ovulating?

No. The average shift in threshold studies is small, several studies found none, and the effect was measured with lab odours at controlled concentrations. Noticing a sharper nose on a given day is not evidence of ovulation, and you cannot use it to avoid or plan a pregnancy.

Is a heightened sense of smell an early sign of pregnancy?

It is a commonly reported one. The NHS lists being more sensitive to certain smells, such as food or cooking, among early pregnancy symptoms, alongside a strange or metallic taste. A 2014 review in Frontiers in Psychology found that most pregnant women report a sharper nose but that threshold tests generally do not confirm it, so the change is probably in how odours feel rather than in raw sensitivity. If a period is late, a pregnancy test taken at the right time answers the question; a smell change does not.

Does the pill change my sense of smell?

Possibly, a little. The 2013 Chemical Senses study found that longer use of oral contraception went with better scores on olfactory tests, but it included only 20 pill users and measured performance rather than how smells felt. Nobody should start or stop contraception on the strength of it.

Why does my period smell stronger some months?

Menstrual blood mixes with vaginal fluid, sweat and whatever is in a pad or cup, and how long a product has been worn makes a large difference. A metallic or slightly musty smell during bleeding is ordinary. A fishy smell that gets worse during the period is one of the patterns ACOG describes for bacterial vaginosis and is worth a swab.

A change to notice, not to fix

Your nose almost certainly does shift across the month, by a modest amount that researchers can measure but you may or may not feel. Your own scent shifts too, through sweat and fluid, and more so in perimenopause. Neither needs a product. The smells that do need attention are the strong or fishy ones, and those have tests and treatments rather than hormonal explanations.

Flowy keeps a free-text note on each day alongside your period dates, so an observation about smell has a date attached when you want to look back at it. It does not predict ovulation from symptoms, diagnose anything, or work as contraception.

This article is for general education only. It is not a diagnosis or a substitute for care from a qualified healthcare professional.